<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>Title</title>
    <style>
      .container {
        height: 300px;
      }

      .left {
        float: left;
        margin-left: -100%;
        width: 200px;
        height: 300px;
        background: red;
      }

      .right {
        float: left;
        margin-left: -200px;
        width: 200px;
        height: 300px;
        background: red;
      }

      .center {
        float: left;
        width: 100%;
        height: 300px;
        background: green;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <div class="center"></div>
      <div class="left"></div>
      <div class="right"></div>
    </div>
  </body>
</html>
